Capacitive mechanical sensor based on elastic electrode, electronic skin and robot

Abstract

The utility model relates to a capacitive mechanical sensor based on an elastic electrode, an electronic skin and a robot. The sensor comprises a base body, a capacitance digital conversion circuit and a processing module, an action electrode is arranged on the surface of the base body and is an elastic bending electrode, one or more static electrodes are arranged above or below the action electrode, the projection of each action electrode relative to the corresponding static electrode at least covers part of the area of the corresponding static electrode, and at least one end of the bending electrode is fixed to the base body for positioning. The other end is bent to form a suspended end far away from the static electrode; the action electrode is isolated from the static electrode through an insulating layer, and the action electrode deforms under the action of external force to change the indirect contact area of the bent part on the static electrode; the capacitance digital conversion circuit is coupled with the corresponding electrode to obtain capacitance between the action electrode and the static electrode; the processing module is coupled with the capacitance digital conversion circuit and used for outputting an electric signal representing the acting force according to the capacitance.

Description

Technical Field

[0001] The utility model relates to tactile perception of a robot, in particular to a capacitive mechanical sensor based on elastic electrodes, an electronic skin, and a robot. Background Art

[0002] Intelligent robots rely on the tactile sensors of the electronic skin on their outer surface to achieve tactile perception and form intelligent responses through the collection and processing of tactile information.

[0003] In terms of tactile sensors, capacitive tactile sensors are currently widely favored by the market due to their many advantages, including high detection accuracy, easy deployment, and low cost. At the same time, existing mature capacitance-to-digital conversion circuits (CDCs), such as the DAI7142 and ADI7147, use a Δ-Σ modulation method to directly convert the measured capacitance value into a digital value by repeatedly charging and discharging the measured capacitance and comparing it with a reference capacitance (see: US Patent Number: 5,134,401). This can increase the capacitance measurement sensitivity to the 1ff level, easily meeting the measurement system's requirements for capacitance measurement sensitivity. They are also immune to stray capacitance. In particular, these chips are designed with multiple channels, making circuit design simple and convenient.

[0004] CN108446042B proposes a capacitive touch sensor and intelligent robot. The multifunctional layer is provided with two layers of electrodes, the upper layer is a cross-shaped common electrode, and the lower layer is four independent electrodes corresponding to the upper cross-shaped common electrode. The upper static electrode constitutes four parallel plate capacitors for measuring the magnitude and direction of three-dimensional force. The solution mainly relies on pressing to generate a change in the distance between the upper static electrodes to change the capacitance. The capacitance change is relatively small, resulting in the sensor's pressure resolution not being particularly good.

[0005] To improve the pressure resolution of detection, CN111896165A proposes a capacitive three-dimensional force vector sensor structure. By using an upper electrode in a multifunctional layer, a four-petal lower electrode below, and an insulating layer in between, the sensor detects the magnitude and direction of three-dimensional force by primarily varying the capacitance based on changes in contact area. This sensor achieves a force resolution of 0.01 grams, surpassing the 0.019 gram force resolution of a human finger. While CN111896165A's three-dimensional force vector sensor structure offers good mechanical resolution, it also has weaknesses: The upper electrode, hanging in an inverted multifunctional layer, forms a downward convex hemisphere within the layer to contact the insulating layer above the lower electrode. The upper electrode must be both flexible and resilient, requiring it to be made of conductive rubber. After pressure is applied, the center of the conductive rubber's downward convex sphere struggles to accurately return to the center of the four-petal lower electrode, leading to a tendency for the center reference to deviate. This problem is exacerbated by wear and aging of the conductive rubber contact surface over long periods of time. Utility Model Content

[0006] The utility model realizes tactile sensing detection based on capacitance technology, achieves layout and cost advantages, and realizes high pressure resolution capability, while solving the problem of center position deviation of pressing rebound.

[0007] To this end, a capacitive mechanical sensor based on elastic electrodes is provided, comprising a substrate, a capacitance-to-digital conversion circuit, and a processing module; an action electrode is arranged on the surface of the substrate, the action electrode being an elastically curved electrode, one or more static electrodes being provided above or below the action electrode, the projection of each action electrode relative to the static electrode covering at least a partial area of ​​the corresponding static electrode, at least one end of the curved electrode being fixed to the substrate for positioning, and the other end being bent to form a suspended end away from the static electrode; the action electrode and the static electrode are isolated by an insulating layer, and the action electrode deforms under the action of an external force to change the indirect contact area of ​​the curved portion on the static electrode; the capacitance-to-digital conversion circuit is coupled to the corresponding electrode to obtain the capacitance between the action electrode and the static electrode; the processing module is coupled to the capacitance-to-digital conversion circuit, and is used to output an electrical signal representing the applied force based on the capacitance.

[0008] As an implementation solution, a first electrode is provided as the action electrode, and a second electrode is provided as the static electrode, and a projection of the first electrode relative to the static electrode covers at least a partial area of ​​the second electrode.

[0009] As another implementation scheme, a first electrode is set as the dynamic electrode, and a second electrode and a third electrode are set as the static electrode. The projection of the first electrode relative to the static electrode at least synchronously covers part of the area of ​​the second electrode and the third electrode, and the shape of the first electrode is configured so that when it is twisted circumferentially by an external force, a difference in the projection area and / or distance relative to the second electrode and the third electrode can be formed.

[0010] As another implementation scheme, a first electrode is set as the static electrode, and at least three electrodes are set as the action electrodes. The action electrodes are distributed circumferentially around the geometric center of the first electrode, and the projection of the first electrode relative to the action electrode at least synchronously covers a portion of the area of ​​each action electrode.

[0011] As another implementation scheme, at least three electrodes are provided in a circumferential distribution for the action electrode, at least one static electrode is provided for each action electrode, and the projection of each action electrode relative to the static electrode covers at least a partial area of ​​the corresponding static electrode. Further, at least two static electrodes are provided for each action electrode, and the projection of the action electrode relative to the static electrode at least synchronously covers a partial area of ​​the corresponding static electrodes, and the shape of the action electrode is configured to form a difference in the projection area and / or distance relative to the corresponding static electrodes when subjected to circumferential twisting by an external force. Further, each action electrode and / or static electrode is formed in an axially symmetrical distribution. Further, a rigid pressure-bearing component for bearing force is included, and the suspended ends of each action electrode are commonly connected to the rigid pressure-bearing component. Further, the action electrode is bent outward or inward relative to the center of its circumferential distribution.

[0012] As another improvement, a shielding electrode is provided on the substrate, arranged around the static electrode and forming a shield by grounding or by coupling a capacitor-to-digital conversion circuit to form an equipotential shield. Furthermore, the active electrode is coupled to the shielding electrode; and / or one end of the active electrode is physically connected to the shielding electrode to provide positioning. Furthermore, the substrate is a circuit board, the static electrode and / or the shielding electrode are printed on the surface of the circuit board, and the active electrode is a metal spring.

[0013] As another improvement, the curved electrode is made of pure elastic material.

[0014] As another improvement, the thickness of the insulating layer is configured to be between 9.8 nanometers and 0.99 millimeters.

[0015] Also provided is an electronic skin comprising the above-mentioned capacitive mechanical sensor.

[0016] A robot is also provided, comprising the electronic skin.

[0017] Compared with the prior art, the advantages of this utility model are:

[0018] Compared with the prior art, the advantages of this utility model are:

[0019] (1) The active electrode is isolated from the static electrode by an insulating layer, resulting in a huge capacitance change caused by the change in contact area of ​​the curved part, thus achieving a high mechanical resolution;

[0020] (2) The action electrode is a curved electrode, and the fixed end plays a positioning role. It uses its own elasticity to press back to the center, restore the center alignment, and maintain the uniformity of the reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The schematic diagram of the mechanical sensor structure using elastic electrodes to measure XYZ three-dimensional forces is given;

[0022] Figure 2 The structure for further measuring torque on the three-dimensional force sensor is given;

[0023] Figure 3 A schematic diagram of the structure in which the action electrode bends outward relative to the center is given;

[0024] Figure 4 A schematic diagram of another mechanical sensor structure using elastic electrodes to measure three-dimensional forces is given;

[0025] Figure 5a A schematic diagram of a mechanical sensor structure using elastic electrodes to measure only normal force is given; and Figure 5b The schematic diagram of the mechanical sensor structure using elastic electrodes to measure normal force and torsion is given. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0027] The capacitive mechanical sensor based on elastic electrodes of the embodiment of the present invention includes a substrate, a capacitance-to-digital conversion circuit, a processing module and an electrode unit. The substrate can be implemented using a circuit board as a carrier. The electrode unit includes an action electrode arranged on the surface of the circuit board. The action electrode is an elastic bending electrode and can be implemented using a bent metal spring. One or more static electrodes are provided above or below the action electrode. The static electrode is fixed to the circuit board, and a metal electrode is formed as a static electrode by printing on the surface of the circuit board. The projection of each action electrode relative to the static electrode covers at least part of the area of ​​the corresponding static electrode, forming an upper and lower distribution and an intersection of the projections. At least one end of the action electrode is fixed to the substrate for positioning. When pressed, it rebounds by its own elasticity, and the other end of the action electrode is bent to form a suspended end away from the static electrode.

[0028] The active electrode and the static electrode are separated by an insulating layer. This insulating layer, such as a coating formed from insulating ink, is thin and reduces the distance between the active electrode and the static electrode. When an external force is applied, the active electrode deforms, changing the indirect contact area of ​​the curved portion on the static electrode—the area where the active electrode presses against the static electrode. A capacitance-to-digital conversion circuit is coupled to the corresponding electrodes to obtain the capacitance between the active and static electrodes. A processing module is coupled to the capacitance-to-digital conversion circuit to output an electrical signal representing the applied force based on the capacitance.

[0029] When the suspended end is subjected to pressure, the active electrode bends downward or pulls sideways in the direction of the force, and the indirect contact area between the bent part and the static electrode changes significantly, and the capacitance value changes. Since there is only a thin insulating layer between the two electrodes, the electrode spacing in the contact area is very small. Such a close distance, coupled with the dielectric constant of the insulating layer being several times greater than that of air, makes the capacitance change based on the significant change in the indirect contact area very large, achieving a higher mechanical resolution; after pressing and releasing, the fixed end of the active electrode is positioned, and the rest of the part elastically returns to the center alignment, maintaining a unified reference.

[0030] As an exemplary implementation, as an improvement, the curved electrode is made of pure elastic material, such as in the form of an elastic metal sheet, which is a further improvement compared to the rubber doped with conductive graphite carbon black or metal particles, which changes the rubber properties, deteriorates the elasticity, and has insufficient rebound speed. As another improvement, the thickness of the insulating layer is configured to be between 9.8 nanometers and 0.99 millimeters. The insulating layer is coated with insulating ink. If the thickness of the insulating ink is 10 microns, the dielectric constant of the insulating ink is 3. According to the capacitance formula C = εr*ε0*A / d, ε0 = 8.854187817x 10-12F / m, ε0 is the vacuum dielectric constant, εr is the relative dielectric constant, and 1mm 2 The contact area capacitance is 886*3=2.66pF. The actual capacitance is the series connection of the air capacitance and the insulating ink. When the distance is 10 microns, the capacitance becomes the series connection of 0.886pF and 2.66pF, which will drop to 0.66pF, a change equivalent to 2pF. According to the high-precision capacitance measurement of the above-mentioned sensing structure, the change can reach 4 million. If MEMS technology is used, the insulating coating can be made into 1um and 0.1mm. 2 Just change.

[0031] To help understand the various possibilities of implementing the above-mentioned solutions, multiple implementation schemes are given below. It should be understood that these solutions are merely illustrations of exemplary structural implementation methods.

[0032] Figure 1A schematic diagram of the structure of a mechanical sensor that uses elastic electrodes to measure XYZ three-dimensional forces is given. The sensor includes a circuit board 101, a static electrode 102, an active electrode 103, and an upper laminate 104. A capacitance detection chip is arranged on the circuit board 101, which integrates a capacitance-to-digital conversion circuit and a processing module. Four fan-shaped static electrodes 102 are printed on the top surface of the board 101. The active electrodes 103 are provided with four circumferentially distributed strip-shaped metal electrodes. Each active electrode 103 corresponds to a fan-shaped static electrode 102, and the projection of each active electrode relative to the static electrode covers at least part of the area of ​​the corresponding static electrode. One end of the active electrode 103 is fixedly connected to the circuit board 101, and the other end is connected to the pressure plate 104. The four active electrodes 103 jointly support and lift the pressure plate 104, and the curved part of the active electrode 103 presses on the static electrode 102 to form indirect contact. When the pressure plate 104 is subjected to vertical pressure, the action electrode 103 bends downward with the pressure plate, the contact area with the fan-shaped electrode increases, and the capacitance value increases; when the pressure plate 104 receives horizontal pressure, the action electrode 103 is pulled sideways with the pressure plate, and the contact area between the four action electrodes and the fan-shaped electrode changes differently, thereby determining the direction and magnitude of the horizontal pressure. In the above description, the pressure plate 104 serves as a rigid pressure-bearing component for bearing force, and the suspended ends of each action electrode 103 are connected to the rigid pressure-bearing component together, so that the sensor returns to its normal position and is corrected together under the interaction of multiple action electrodes 103. Each action electrode 103 and / or static electrode 102 is distributed axially symmetrically, forming a uniform distribution to improve sensor accuracy.

[0033] Furthermore, the pressing can be set to achieve the change from line contact to surface contact, forming a large multiple of the area change of the front and rear indirect contact areas during the pressing process, further expanding the range of capacitance value change.

[0034] Figure 2 The structure for further measuring torque on a three-dimensional force sensor is shown. Each action electrode 103 is provided with at least two static electrodes 1021 and 1022, and the projection of the action electrode relative to the static electrode at least synchronously covers a portion of the area corresponding to each static electrode. The shape of the action electrode is configured so that when subjected to circumferential torsion by an external force, a difference in the projection area and / or distance relative to each corresponding static electrode can be formed. Specifically, each action electrode 103 is provided across two fan-shaped electrodes in the width direction. When the pressure plate 104 is subjected to vertical pressure, the action electrode 103 bends downward with the pressure plate, and the indirect contact area with the electrodes 1021 and 1022 increases, and the capacitance value increases. When the pressure plate 104 is subjected to circumferential force, the action electrode 103 is subjected to circumferential torsion with the pressure plate, and the capacitance C1 formed by the action electrode 103 and the static electrode 1021 and the capacitance C2 formed by the action electrode 103 and the static electrode 1022 differ from each other. The torque can be obtained based on the difference.

[0035] Further, see Figure 1 、 Figure 2 A printed shielding electrode 105 is provided on the substrate 101. The shielding electrode 105 surrounds the static electrode 102 and forms a shield by grounding or by coupling a capacitor-to-digital conversion circuit to form an equipotential shield, thereby improving the anti-interference capability of mechanical measurements. Preferably, the active electrode 103 is coupled to the shielding electrode 105 to jointly shield the static electrode 102. In this case, the active electrode 103 acts as part of the shielding electrode to enhance sensor stability. Alternatively, one end of the active electrode 103 is directly physically connected to the shielding electrode to achieve positioning, thereby simplifying the structure and ensuring stability.

[0036] As an example, the action electrode 103 can be set as follows Figure 1 or Figure 2 As shown, the center of the circumferential distribution of each action electrode is bent inward, and can also be set as follows Figure 3 The center of the circumferential distribution is shown to be bent outward. In this case, the shielding electrode 105 is located on the pressure plate 104 and couples with each active electrode. The outward bending solution expands when pressed, forming a larger bending deformation than the inward bending solution. Therefore, the outward bending solution has the advantage of a wider range.

[0037] Figure 4 A schematic diagram of another mechanical sensor structure using elastic electrodes to measure three-dimensional force is provided. Specifically, the structure is relatively simplified. A static electrode 102 is printed on the top surface of a substrate 201. The static electrode 102 is arranged in a circular ring as the first electrode. Four active electrodes 203 are arranged, each circumferentially distributed around the geometric center of the first electrode. The projection of the first electrode onto the active electrode simultaneously covers at least a portion of the area of ​​each active electrode. The suspended ends of each active electrode 203 jointly support a pressure plate 204, with the bent portions of the active electrodes 203 pressing against the static electrode to form indirect contact. When the pressure plate 204 is subjected to vertical pressure, the active electrodes 203 bend downward with the pressure plate, increasing the contact area between each active electrode 203 and the static electrode and increasing the capacitance. When the pressure plate 204 is subjected to horizontal pressure, the active electrodes 203 are pulled sideways with the pressure plate. The indirect contact area between the four active electrodes and the static electrode changes differently, resulting in differences in the four capacitance outputs formed by the four active electrodes with the static electrode. This difference is used to determine the direction and magnitude of the horizontal pressure.

[0038] In some cases where only the normal force needs to be measured, the sensor can be further simplified. Figure 5a A schematic diagram of a mechanical sensor using elastic electrodes to measure only normal force is provided. The active electrode is a first electrode 301, and the static electrode is a second electrode 302. The projection of the first electrode relative to the static electrode covers at least part of the area of ​​the second electrode. When the pressure plate is subjected to vertical pressure, the first electrode 301 bends downward with the pressure plate, increasing the indirect contact area with the second electrode 302 and the capacitance value.

[0039] Figure 5b A schematic diagram of a mechanical sensor structure using elastic electrodes for measuring normal force and torque is provided. The active electrode is a first electrode 301, and the static electrodes are a second electrode 3021 and a third electrode 3022. The projection of the first electrode 301 relative to the static electrode simultaneously covers at least a portion of the area of ​​the second electrode 3021 and the third electrode 3022. The shape of the first electrode 301 is configured so that, when subjected to circumferential torsion by an external force, it can create a difference in the projected area and / or distance relative to the second electrode 3021 and the third electrode 3022. When the pressure plate is subjected to vertical pressure, the first electrode 301 bends downward with the pressure plate, increasing the indirect contact area with electrodes 3021 and 3022 and the capacitance value. When the pressure plate is subjected to circumferential force, the first electrode 301 twists circumferentially with the pressure plate, forming two capacitance values ​​with 3021 and 3022, respectively, which can be used to further measure torque.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit the scope of protection of the utility model. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the utility model.

Claims

1. A capacitive force sensor based on elastic electrodes, characterized in that: It includes a substrate, a capacitance-to-digital conversion circuit, and a processing module; An action electrode is provided on the surface of the substrate. The action electrode is an elastically curved electrode. One or more static electrodes are provided above or below the action electrode. The projection of each action electrode relative to the static electrode covers at least a portion of the area of ​​the corresponding static electrode. At least one end of the curved electrode is fixed to the substrate for positioning, and the other end is bent to form a suspended end away from the static electrode. The moving electrode and the static electrode are isolated by an insulating layer. When the moving electrode is deformed under the action of external force, the indirect contact area of ​​the bending part on the static electrode is changed. The capacitance-to-digital conversion circuit is coupled to the corresponding electrodes to obtain the capacitance between the action electrode and the static electrode; The processing module is coupled to a capacitance-to-digital conversion circuit and is configured to output an electrical signal representing the applied force according to the capacitance.

2. The capacitive force sensor according to claim 1, wherein: The action electrode is provided with a first electrode, the static electrode is provided with a second electrode, and the projection of the first electrode relative to the static electrode at least covers a part of the area of ​​the second electrode.

3. The capacitive force sensor according to claim 1, wherein: The action electrode is provided with a first electrode, and the static electrode is provided with a second electrode and a third electrode. The projection of the first electrode relative to the static electrode at least synchronously covers part of the area of ​​the second electrode and the third electrode, and the shape of the first electrode is configured so that when it is twisted circumferentially by an external force, it can form a difference in the projection area and / or distance relative to the second electrode and the third electrode.

4. The capacitive force sensor according to claim 1, wherein: The static electrode is provided with a first electrode, and the action electrode is provided with at least three electrodes. The action electrodes are distributed circumferentially around the geometric center of the first electrode, and the projection of the first electrode relative to the action electrode at least synchronously covers a part of the area of ​​each action electrode.

5. The capacitive force sensor according to claim 1, wherein: The action electrodes are provided with at least three electrodes distributed circumferentially, each action electrode is provided with at least one static electrode, and the projection of each action electrode relative to the static electrode at least covers a part of the area of ​​the corresponding static electrode.

6. The capacitive force sensor according to claim 5, wherein: At least two static electrodes are arranged corresponding to each active electrode, and the projection of the active electrode relative to the static electrode at least synchronously covers a portion of the area of ​​each corresponding static electrode. The shape of the active electrode is configured so that when it is subjected to circumferential twisting by an external force, it can form a difference in the projection area and / or distance relative to each corresponding static electrode.

7. The capacitive force sensor according to claim 4, 5 or 6, characterized in that: The active electrodes and / or static electrodes are distributed in an axisymmetric manner.

8. The capacitive force sensor according to claim 5 or 6, characterized in that: It comprises a rigid pressure-bearing component for bearing force, and the suspended ends of each action electrode are commonly connected to the rigid pressure-bearing component.

9. The capacitive force sensor according to claim 5 or 6, characterized in that: The active electrodes are bent outward or inward relative to the center of their circumferential distribution.

10. The capacitive force sensor according to any one of claims 1 to 6, characterized in that: A shielding electrode is provided on the substrate, which is arranged around the static electrode and forms a shield by being grounded or forms an equipotential shield by a coupling capacitor digital conversion circuit.

11. The capacitive force sensor according to claim 10, wherein: The action electrode is coupled to the shielding electrode; And / or, one end of the action electrode is physically connected to the shielding electrode to form the positioning.

12. The capacitive force sensor according to claim 11, characterized in that: The substrate is a circuit board, and the static electrode and / or the shielding electrode are printed on the surface of the circuit board; The action electrode is a metal dome.

13. The capacitive force sensor according to claim 1, wherein: The curved electrodes are made of pure elastic material.

14. The capacitive force sensor according to claim 1, wherein: The thickness of the insulating layer is configured to be between 9.8 nanometers and 0.99 millimeters.

15. An electronic skin, characterized in that: The device comprises a capacitive mechanical sensor according to any one of claims 1 to 14.

16. A robot, characterized in that: Comprising the electronic skin as described in claim 15.

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